1. Field of the Invention
The present invention relates to a cab supporting structure of a work vehicle such as a construction machine, and particularly relates to a cab supporting structure capable of ensuring safeness even when a high impact force acts on the cab.
2. Description of the Related Art
Generally, as shown in FIG. 17, a hydraulic shovel as the construction machine is provided with a lower driving body 81 and an upper swing body 82 that is swingably attached to this lower driving body 81 via a swing mechanism. Then, a cab (cabin) 83 is attached to this upper swing body 82 and at this cab's 83 side, a work equipment 84 is projected from the upper swing body 82.
In order to absorb shock to the cab 83 while the vehicle is driving and to improve a ride quality, conventionally, the cab 83 is supported by a vehicle body frame via an attenuation mechanism. As this attenuation mechanism to absorb the shock, an antivibration member made of an elastic body may be used (for example, refer to patent documents 1, 2, 3 and 4).
As shown in FIG. 18, the conventional cab supporting structure disclosed in the patent document 1 is provided with an antivibration member 86 to be attached to the cabin's (cab's) 83 side, a positioning member 87 to be attached to this antivibration member 86, and an acceptance member 89 to be attached to a frame 88's side. In other words, the positioning member 87 is attached to the antivibration member 86 via a bolt member at its upper wall 87a, and a through-bore 90 is provided on its lower wall 87b. The acceptance member 89 has a projection 91, and this projection 91 is attached to the lower wall 87b via the bolt member with this projection 91 fitted in the through-bore 90 of the lower wall 87b. Thereby, the cab 83 is accepted by the frame 88 via the antivibration member 86 so as to absorb the vibration from the frame 88's side.
As shown in FIG. 19, the conventional cab supporting structure disclosed in the patent document 2 is provided with a lower side member 93, an upper side member 94, and a coupling member 95 (composed of a bolt member 103 and a nut member 107) to couple this lower member 93 with the upper side member 94. In other words, the lower side member 93 has a base 96 and a column portion 97 that is constructed from this base 96. On this base 96, an elastic body 98 is mounted. On the column portion 97, a long hole 99 that is elongated vertically is provided, and in this long hole 99, an elliptic ring-type elastic body 100 is fitted. Then, the upper side member 94 has a base 101 and a main portion 102 constructed from this base 101, and the main portion 102 is provided with a through-bore 104 into which a bolt member 103 of the coupling member 95 is inserted. In this case, the lower opening of the column portion 105 at the cab's 83 side is fitted into the main portion 102 of the upper side member 94, the bolt member 103 is inserted into through-bores 106 of this column 105, a through-bore 104 of the main portion 102, and the elastic body 100 of the lower side member 93 so as to engage a nut member 107 into this bolt member 103 by a screw. Therefore, the upper side member 94 is accepted by the elastic body 98 of the lower side member 93 and the bolt member 103 is inserted into the elastic body 100, and thereby, these elastic bodies 98 and 100 are made antivibration members, and the lower side member 93 can elastically accept the upper side member 94 so as to absorb the shock.
As shown in FIG. 20, the conventional cab supporting structure disclosed in the patent document 3 is provided with a pair of elastic bodies 111 to be arranged at the frame 88's side, and a pair of acceptance bodies 112 and 113 clipping these elastic bodies 111. In other words, a through-bore 114 is provided through the frame 88, the elastic bodies 111 are partially fitted into this through-bore 114, and a bolt member 115 to be inserted into these acceptance bodies 112 and 113 is engaged into the cab 83's side by a screw with the elastic bodies 111 clipped by the acceptance bodies 112 and 113. Thereby, the cab 83 may be elastically accepted by the frame 88. When the cab 82 is shifted (moved) to the frame's 88 side, a flange portion 116 of the acceptance body 113 may contact the frame 88 so as to regulate the further shift of this cab 83 toward the frame 88's side.
As shown in FIG. 21, the conventional cab supporting structure disclosed in the patent document 4 is provided with a case 120, a stud 121 to be received in this case 120, and an attenuation plate 122 to be received in the case 120 as coupled with this stud 121. In other words, the case 120 is composed of a tubular body 123 opening vertically, and a container 124 arranged at the lower side of this tubular body 123 and forming a reception chamber of the attenuation plate 122. An elastic body 125 to be fitted into the tubular body 123 of the case 120 is externally fitted to the stud 121 and viscosity liquid 126 is injected into the container 124. Then, a screw portion 127 projected from a stud 121 is fitted into the cab side by the screw and the case 120 is attached to the frame side. A stopper 128 is projected at the upper end of the tubular body 123 of the case 120, and at the same time, a stopper 129 is constructed on this stopper 128. A stopper 130 outwardly extending in the a radial direction is provided at the lower side of the tubular body 123.
In this attenuation mechanism shown in FIG. 21, when the stud 121 vibrates against the case 120, the viscosity liquid 126 is disarranged by this vibration, and due to the viscosity resistance of this viscosity liquid 126 and the attenuation plate 122, the absorption function may be effected so as to attenuate the vibration. When the stud 121 tilts toward the case 120, the cab side may abut against the stopper 129 and at the same time, the attenuation plate 122 may abut against the stopper 130 so as to prevent the cab side from further tilting of the cab side.    [Patent Document 1]    JP-A-2001-39352 (pages 2-3, FIG. 2)    [Patent Document 2]    U.S. Pat. No. 3,868,190 (third to fourth column, FIG. 2)    [Patent Document 3]    JP-A-11-310167 (pages 32-34, FIG. 2)    [Patent Document 4]    JP-A-10-26172 (page 3, FIG. 1, FIG. 3)
Even if the construction machine falls down, or the construction machine crashes into a rock and a tree or the like, the high impact force may act on the cab 83. Therefore, in order to secure an operator from such impact force, recently, a cab corresponding to a ROPS (Roll Over Protective Structure) having a protection function has been used. An availability of the above-described each conventional example has been examined with respect to the case that the above-described high impact force (hereinafter, refereed to as a ROPS load) acts on the cab 83. At first, according to the conventional cab supporting structure disclosed in the patent document 1 shown in FIG. 18, if the impact force acts in a direction separating the cab side from the frame 88, there is no regulation means for the shift of the cab 83 and the cab 83 is highly displaced, so that the conventional cab supporting structure disclosed in the patent document 1 cannot be provided for the ROPS. According to the conventional cab supporting structure disclosed in the patent document 2 shown in FIG. 19, if the cab's 83 side is displaced in a direction separating the cab's 83 side from the frame's 88 side, the bolt member 103 of a coupling body 25 may abut against the elastic body 100 of the lower side member 93 against this displacement, and this displacement can be regulated, however, if the ROPS load acts in the direction separating the upper side member 94 from the lower side member 93, this load can barely supported and it is feared that the elastic body 100 may be damaged. Therefore, the conventional cab supporting structure disclosed in the patent document 2 cannot be provided for the latter case.
Next, according to the conventional cab supporting structure disclosed in the patent document 3 shown in FIG. 20, with respect to the displacement in the direction approaching the frame's 88 side of the cab's 83 side, the flange portion 116 of the acceptance body 113 may contact the frame 88 so as to regulate the further displacement of this cab 83 toward the frame's 88 side. However, on the contrary, if the ROPS load acts in the direction separating the cab side from the frame's 88 side, this load is allowed to be supported, however, the lower elastic body 111 is compressed by the frame 88 and the acceptance body 112 and it is feared that the elastic body 111 and the acceptance body 112 are damaged. Therefore, the conventional cab supporting structure disclosed in the patent document 3 cannot be provided for the latter case.
According to the conventional cab supporting structure disclosed in the patent document 4 shown in FIG. 21, with respect to the displacement in the direction approaching the cab side to the frame side, the cab side may abut against the stopper 129 so as to regulate the further displacement of this cab toward the frame's 88 side. With respect to the displacement in the direction separating the cab side from the frame side, the attenuation plate 122 may abut against the stopper 130 so as to regulate the further displacement of this cab in the direction separating from the frame's 88 side. The conventional cab supporting structure shown in FIG. 21 is preferably used for the cab corresponding to the ROPS. However, since the regulation means (stopper) is provided in this attenuation mechanism (liquid sealed type mounting) itself in this case, the configuration of this attenuation mechanism becomes complex and the attenuation mechanism should be larger and heavier and it becomes too expensive. Accordingly, the cab corresponding to the ROPS using such a special attenuation mechanism should be also expensive.